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Review: Chemical Properties  Related to internal makeup of substances  Describe how a substance reacts with other substances to form new substances Chemical Changes  Mixtures and solutions are formed through physical changes  compounds are formed through chemical changes  A compound is a combination of two or more substances that are chemically combined

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A chemical reaction in trees causes the leave to change colors 1. A Color Change Signs of a Chemical Change

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When substance undergo a chemical change, often a new substance that smells different than the original substances is produced. Ex. Rotting meat or sour milk 2. Something Smells Signs of a Chemical Change

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The appearance of bubbles or fuzzing means that a gas is being produced Ex. Vinegar and Baking Soda produce Carbon Dioxide 3. The Presence of Bubbles or Frizzing Signs of a Chemical Change

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When a glow stick is bent, a capsule inside breaks, causing the chemicals within the capsule and the stick to react and give off light. 4. Light is Given Off Signs of a Chemical Change

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Burning is a chemical reaction that releases heat energy Photosynthesis is a chemical reaction that absorbs heat energy from the sun. 5. A Change in Temperature Signs of a Chemical Change

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In some chemical changes, two liquids react and form a new liquid and a solid (precipitate). 6. A Precipitate Forms Signs of a Chemical Change

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A chemical change is very difficult or impossible to reverse. Ex. Once you bake a change, you can never change the cake to batter 7. It’s Permanent Signs of a Chemical Change

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Although most of these signs indicate a chemical change, there are exceptions to the rule. Boiling water produces water bubbles but this is a PHYSICAL change Adding food coloring to water results in a color change, but it’s just a PHYSICAL change. CAUTION